During the past years, the interest in radio access technologies for providing services for voice, video and data has increased. The communication devices that support these services, for example, mobile cellular units, include a transmitting component for transmitting information associated with voice, video and/or data to a base station (for example the base station of a telecommunication network) and a receiving component for receiving information associated with voice, video and/or data received from the base station.
FIG. 1 shows a communication device 10 that includes such a transmitting component 12 and a receiving component 14. The two components may be connected to a circulator 16. The circulator 16 may switch a connecting path of either the transmitter or receiver to a common antenna 18. The circulator 16 passes a transmit signal to the antenna with low attenuation, but should not pass the transmit signal to the receiver. A limitation of using such a circulator is that transmit power reflected by the antenna or leaked directly from a power amplifier of the transmitter may be conducted by the circulator 16 to the receiver as the circulator cannot completely close a communication path between the transmitter and the receiver. This may damage the receiver because the receiver is not designed to handle the high energy signals generated by the transmitter.
To protect the receiver from such high energy signals, a low-ohmic switch 19 may be used in addition to the circulator 16, to prevent the high energy signal entering the receiver 14. The switch 19 may be implemented by using a large MOSFET. However, a drawback of this solution is that the MOSFET might introduce losses in the signal path that degrade the receiver characteristics when the receiver is on, which is undesirable. In addition, another drawback is the amount of space needed to accommodate the large MOSFET and the cost for adding the MOSFET, especially since modern mobile communication devices have limited amounts of available space and are sensitive to cost.
Accordingly, it would be desirable to provide devices and methods for insulating the receiver from the transmitter that avoid the afore-described problems and drawbacks.